Begin by exporting the data you want to transfer from your PostgreSQL database. You can use the `pg_dump` utility to accomplish this. For instance, to export a specific table, execute:
```bash
pg_dump -U [username] -h [hostname] -d [database] -t [table_name] -F c -f [file_name].sqlc
```
This command exports the table in a compressed format, which you will use later.

Once exported, prepare the data for transfer by decompressing it if necessary, and converting it into a format that can be easily ingested by Starburst Galaxy, such as CSV. Use `pg_restore` to convert it:
```bash
pg_restore -U [username] -d [database] -t [table_name] -f [file_name].csv [file_name].sqlc
```
Ensure that the CSV format aligns with the expected schema in Starburst Galaxy.

Starburst Galaxy can access data from cloud storage services like AWS S3, Google Cloud Storage, or Azure Blob Storage. Upload your CSV file to a suitable bucket in your chosen cloud storage. Use the cloud provider's CLI or web interface to perform the upload.

In Starburst Galaxy, create an external table that references the data in your cloud storage. This involves writing a table definition that specifies the location and format of your data. For example:
```sql
CREATE TABLE your_schema.your_table (
column1 datatype,
column2 datatype,
...
)
WITH (
external_location = 's3://your-bucket/your-file.csv',
format = 'CSV'
);
```
Replace the `external_location` with the path to your file in the cloud storage.

Once your external table is set up, validate that Starburst Galaxy can access and read the data correctly. Execute a simple `SELECT` query to ensure the data is correctly populated:
```sql
SELECT * FROM your_schema.your_table LIMIT 10;
```
Check for any discrepancies or errors in the data retrieval process.

If transformations are needed, perform them using SQL within Starburst Galaxy. For example, you can create a new table with transformed data:
```sql
CREATE TABLE your_schema.transformed_table AS
SELECT column1, column2, ... FROM your_schema.your_table WHERE condition;
```
This step allows you to clean or modify the data as needed before final usage.

Finally, verify the integrity of the data in Starburst Galaxy by comparing it with the original data in PostgreSQL. Conduct comprehensive checks on row counts and specific data points. Once verified, clean up any temporary files or tables used during the transfer process to maintain an efficient environment.
By following these steps, you can successfully move data from PostgreSQL to Starburst Galaxy without relying on third-party connectors or integrations.